Localization method and device for determining the degree of fragmentation of stones

ABSTRACT

The disclosure relates to apparatus for localizing the fragments of stones associated to a lithotrite comprising a spherical focussing cup acting as a power transducer and an auxiliary transducer subjected to a sectorial scanning and mounted at the center of the cup and coupled to an echography device. The apparatus comprises an auxiliary generator for exciting the power transducer with pulses generated at a frequency of a few hertz and at a power reduced with respect to that of the shootings. During the emission of the pulses with reduced power, the receiver of the echographic device is connected to an auxiliary cathode tube which forms an A echography image in order to localize the fragments of stones.

CROSS REFERENCE TO PRIOR APPLICATIONS

This application is a continuation-in-part of Ser. No. 073,369, filedApr. 13, 1987now abandoned which is a division of Ser. No. 728,905,filed Apr. 30, 1985 now U.S. Pat. No. 4,658,828, which claims anybenefits to which it is entitled under 35 U.S.C. 120 on the basis ofU.S. Pat. No. 4,617,931.

During the use of an extracorporeal lithotriptor for destroying gallstones by pressure waves, the degree of fragmentation thereof, theknowledge of which is important for determining the moment when thefiring should be stopped, is somtimes difficult to assess.

In fact, from the very beginning of fragmentation, small fragments maybe deposited under the stone and form a screen in front of the locatingdevice, for example an echography device, which the lithotriptorcomprises. The image which then appears on the screen of this device isthat of the layer formed by the fragment which then merges with the restof the stone. The resolution of the device is not sufficient to separateeach elementary particle and the operator, deceived by the aspect of theimage, may stop the treatment prematurely.

Another case of error is that in which, with the gall stone enclosed ina cavity, the fragments remain in position. The result is that theechographic image may remain unchanged even when the fragmentation iscomplete.

The invention has as an object a method of locating the stones andfragments thereof comprising the formation of an image and observationthereof in real time, characterized in that said fragments are subjectedto pulsed and focused elastic waves emitted with a relatively smallpower with respect to that of the firing, but appreciably higher thanthat used for the echography, and at a rate of the order of a few hertz,advantageously 5 to 10 Hz and in that the shape modifications undergoneby the echoes of the fragments are interpreted so as to obtaininformation relative to the size of the fragments.

The invention is based on the discovery that small sized fragments (lessthan 3 mm for example), subjected to such an elastic wave, undergo amovement of an amplitude inversely proportional to their size. Becauseof interference phenomena there partly results therefrom a substantialand characteristic modification of the shape of the echoes reflected bythe fragment. The echo may disappear completely if the size of thefragment is less than a certain limit, it will on the other hand bestable for a fragment of a size greater than a given threshold.

In a preferred embodiment, the stone and its fragments subjected to saidelastic waves are observed with type A echography effected on a linewhich passes through the focal spot of the elastic wave beam and thedisappearance or modification of the echo are observed on each of thefragments for indicating that the above mentioned lower limit of sizehas been reached and that it is no longer necessary to resume firing.

In an improvement, a zone containing fragments whose sizes it is desiredto analyse more finely is subject, during application of said elasticwaves, to elastic examination pulses and the variation of the carrierfrequency of these examination pulses by reflection from the fragmentsis measured so as to give an indication of the speed of movement of saidfragments under the impact of said elastic waves.

The invention also has as an object a device for implementing the abovementioned process. In its preferred embodiment, this device uses themain ultrasonic pulse emitter of the lithotriptor at reduced power andat a pulse rate appropriate to setting in motion the gall stonefragments and displays the echoes in echography A.

Other characteristics, as well as the advantages of the invention, willclearly appear from the light of the following description.

The single FIGURE of the accompanying drawing is the general diagram ofa lithotriptor equipped with an apparatus for locating gall stonefragments in accordance with a preferred embodiment of the invention.

A transducer 1 has been shown in the drawing in the form of a sphericalskull cap, constructed and mounted so as to be able to be positionedalong three orthogonal axes, as was described in U.S. Pat. No.4,617,931, filed on Nov. 26, 1984 in the name of Jacques Dory for:"Ultrasonic pulse apparatus for destroying calculuses" and which isincorporated in the present disclosure as a part thereof. An auxiliarytransducer 2 is fixed to the center of the spherical skull cap andincludes an oscillating piezoelectric element 200 controlled by a motor201, itself controlled by an electronic circuit 4.

The transducer 1 is energized by a pulse emitter 3 one input 30 of whichfor adjusting the peak power emitted is connected, through a switch 300,either, in position I, to a member 301 which allows said power to beregulated to a value appropriate for lithotrity (of the order of 100 Kwfor example), or, in position III, to a member 300 which fixes saidpower at a much lower value appropriate to fragmentation location (ofthe order of 10 to 20 Kw for example), or finally, in position II, to amember 302 which fixes said power at a still more reduced value, of theorder of a few watts. The construction of the members shown symbolicallyby the rectangles 301 to 303 is within the scope of a man skilled in theart. So as to obtain the power of a few watts, block 302 must cause aconsiderable reduction of the power supply voltage of the emitter.

The waves generated by emitter 3 have for example a high frequency of500 KHz and are emitted, depending on whether switch 33 occupies thepositions I, II or III, either as pulses of a few μs durationsynchronized by circuit 4 as will be explained further on, or in theform of 256 pulses spread out over a duration of 1/10 s whichcorresponds to a complete oscillation of element 200, or finally in theform of brief pulses at a rate of 5 to 10 Hz.

Circuit 4 generates saw tooth voltage signals comprising successivelyportions of 1/10th of a second with increasing slope and portions of1/10th of a second with decreasing slope. These portions, which controlthe rotation of motor 201 in one direction then in the other forproviding sectorial scanning of angle θ, are separated from each otherby intervals of 1/100 th second during which a control is fed to output34. Therefore, when the switch 33 is in position I, said controls arereceived at the synchronization input 36 of the emitter 3, whichtriggers off a burst of firing. On the other hand, when switch 33 is inposition II the input 36 is connected to a generator 211 which delivers256 pulses during said portions of 1/10th second. Finally, when switch33 is in position III, the input 36 is connected to a member 360 whichsynchronizes the emitter to a pulse frequency of 5 to 10 Hz.

Furthermore, the generation of saw teeth by circuit 4 is controlled by aswitch 40: the saw teeth are generated when this switch is in position401, and interrupted when it is in position 402. The scanning bytransducer 2 is then stopped in the median position of the beam.Simultaneously the memory 24 which receives the echoes from transducer2, passing through an amplifier 22 and through an analog-digitalconverter 23, is then locked in the "read only" position, by means of aswitch 240 which is coupled (in a way not shown) to switch 40 which isthen in position 2402.

When switch 40 is on the other hand in position 401, switch 240 is inposition 2401 and memory 24 operates for writing and reading: thesignals received at 22 are stored line by line in memory 24, a writingaddress device 25, controlled by circuit 4, causing the respectivedeflection angles of the beam emitted and/or received by transducer 2 tocorrespond with the respective lines of the memory. A device 26 forrapid reading of the memory energizes the X and Y deflection coils of acathode ray tube 28, so the brilliancy control electrode receives thecorresponding contents of memory 24, transformed into an analog signalby a digital-analog converter 27.

Transducer 2 is connected to a very high frequency pulse emitter (5 MHzfor example) 21 synchronized either by the pulse generator 211 whenswitch 210 is in position I, or grounded when switch 210 is in positionII or III (these positions I to III being obtained at the same time asthe corresponding positions of switches 33 and 300). In the positions IIor III of the switches, emitter 21 is therefore not in service andtransducer 2 only operates for reception when a size control pf thefragments by echography A is effected.

The signal from amplifier 22 is applied to the vertical deflectioncontrol of the beam of a second cathode ray tube 45, whose horizontaldeflection control is provided by a generator 44. This latter is itselfsynchronized by generator 211, with an adjustable delay delivered by adelay circuit 43. Members 43 and 44 are adjusted so that a small portiononly of the zone of the body containing the stone K is displayed on thescreen of the cathode ray tube 45.

By way of example, if the gall stone is at a depth of 100 mm, the tubewill only display a zone corresponding to a depth of 20 mm, and thedelay will be adjusted so as to correspond to a distance of 90 mmtravelled by the elastic waves. The zone effectively displayed will thusbe limited by depths between 90 and 110 mm.

The operation of the device which has just been described is as follows:

When switches 33, 300 and 210 are in position I, high power pulses aregenerated by transducer 1 and focused at the center F of the sphere.

For the duration of each portion of 1/10th second, the sectorial scanechography device formed by the transducer, the auxiliary emitter andthe reception, processing and display means 22 to 27, displays on thescreen of the cathode ray tube 28 an image of the scanned region of thebody including the kidney and the gall stone K.

Furthermore, the display device is adapted, in a way known per se, so asto materialize on the screen of the cathode ray tube (for example by across) the theoretical position of the focal spot in the sectional planeshown, which plane passes through the axis of symmetry of transducer 1.(As a B Scan is effected in an axial plane). The operator begins bymoving transducer 1 along X until the stone appears clearly on thescreen, then he moves it along Y and Z until the cross coincides withthe central region of the image of the stone. At this time, the switchesmay be put into position II; the region of the focal spot is then madevisible on the screen, with a luminosity proportional to thecorresponding energy concentration. Thus a representation is obtained ofwhat the distribution of the energy of the shock wave will be duringfiring, which allows the adjustments to be checked and completed.

When it is desired to check the fragmentation, the switches are movedfrom position I to position III and switch 40 to position 402. Theresult is that scanning is stopped on the median line and, with switch240 itself in position 2402, the cathode ray tube 28 continues todisplay the gall stone. Moreover, transducer 1 then works at reducedpower and at a rate of 5 to 10 Hz, which results in causing agitation ofthe stone fragments.

The echoes resulting from the reflection of the pulses emitted bytransducer 1 are received by transducer 2 and are transmitted to thehorizontal deflection control of the cathode ray tube 45 whoseluminosity control electrode is subjected to a DC voltage adjustable bymeans of a potentiometer 450. Thus an echography A of the stone isobtained, on a scale such that the image of the fragments will beclearly visible. This image is also provided not only when the switchesare in position I but also when they are in position III and,consequently, going over from position I to position III allows eitherthe absence of deformation, or the deformation or even the disappearanceof the image to be observed for each fragment.

During lithotrity the progressive reduction in size of the fragments maythus be monitored by making the successive switchings from I to III.

At 50 has been shown a conventional Doppler device which emits a pulsedwave of very high carrier frequency (5 MHz for example) transmitted totransducer 2 and which receives the corresponding echoes coupled by thetransducer 2. When it is desired to bring this device into service,switches 33, 210 and 300 are placed in position III and scanning isstopped in the median position of the beam emitted by transducer 1,switch 40 being for this purpose in position 402.

In position III, the transducer 1 emits pulsed waves at the frequency of500 KHz with reduced power with respect to that of the firing. The rateof these pulses is also defined by generator 360.

It is preferably arranged of this rate to be a sub multiple of the rateof the Doppler pulses: this latter being for example 5000 Hz, that ofthe reduced power pulses for agitating the fragments may be 5-10-20 or50 Hz. The relative setting of the two pulse trains may then be suchthat a Doppler pulse arrives on the fragment at the same time as anagitation pulse.

The Doppler echoes are only received during a time interval defined by asquare wave generated inside device 50 in a way known per se. Thissquare wave is applied, as well as the signal read out from memory 24(while switch 240 is position 2402), to a mixer 502 whose output drivesthe luminosity control electrode of the cathode ray tube 28. Thus, onthe screen of said tube, the position of an adjustable window ismaterialized for selecting one or more fragments.

The low frequency Doppler signal generated by device 50, and whoseamplitude is proportional to the speed of movement of agitation of thefragment, is applied to a cathode ray tube or a recorder 501, preferablyat the same time as the agitation pulses (applied to the input 5010).Thus, the correlations between these two signals may be observed. Thefrequency of the Doppler signal is inversely proportional to the size ofthe fragments, which permits quantitative observation thereof, if needbe by spectral analysis of the Doppler signal.

The Doppler measurement and location of the fragments by echography Amay be carried out simultaneously.

It goes without saying that different modifications of detail may bemade to the devices described and shown without departing from thespirit of the invention. One of the means for detecting the size of thefragments may even be omitted or else, echography A may be replaced byanother image forming means in real time, for example an X ray deviceassociated with a brilliancy amplifier.

I claim:
 1. A method for non invasive fragmentation of a concretionwithin a region of the body of a patient, comprising the steps of:(a)generating, during short pulse periods, an elastic wave beam focusedupon said concretion and having a predetermined high power adapted fordisintegrating the concretion into fragments; (b) radiating a pulsedacoustical signal beam and sweeping the signal beam across said region;(c) detecting echoes of the acoustical signal reflected in said regionand forming real time images of said region by displaying said echoes;(d) stopping the generation of said elastic waves and subjecting saidfragments to further pulsed and focused elastic waves emitted with apower which is substantially lower than said predetermined high powerand sufficient for agitating the fragments, and (e) radiating a furtherpulsed acoustic signal beam directed on the agitated fragments,detecting echoes of said further acoustic signal beam reflected by saidfragments and deriving from said echoes information relative to the sizeof said fragments.
 2. The method of claim 1, wherein the power of saidfurther elastic wave beam does not exceed 20 kilowatts.
 3. The method ofclaim 1, wherein the pulse frequency of said further elastic wave beamis between 5 and 50 Hz.
 4. The method of claim 1, wherein said furtheracoustic signal beam is directed through the focal point of the focusedwave beam, and an A type visual display of said echoes is effected forderiving said information.
 5. The method of claim 4, wherein all steps(a) to (e) are finally stopped when said echoes disappear on said A typevisual display.
 6. The method of claim 1, wherein said further acousticsignal beam is generated from an electric pulsed wave having apredetermined carrier frequency and said information is derived bymeasuring the difference between the carrier frequency of said echoesand said predetermined carrier frequency.
 7. The method of claim 6,wherein said further pulsed acoustic signal beam has a pulse frequencywhich is a multiple of the pulse frequency of said further elastic wavesand the further pulsed signal beam and the further elastic waves aresynchronized.
 8. A method for non invasive fragmentation of a concretionwithin a region of the body of a patient, comprising the steps of:(a)generating, during short pulse periods, and elastic wave beam focusedupon said concretion and having a predetermined high power adapted fordisintegrating the concretion into fragments; (b) radiating a pulsedacoustical signal beam and sweeping the signal beam across said region;(c) detecting echoes of the acoustical signal reflected in said regionand forming real time images of said region by displaying said echoes;(d) stopping the generation of said elastic waves and subjecting saidfragments to further pulsed and focused elastic wave emitted with apower which is substantially lower than said predetermined high powerand sufficient for agitating the fragments, and (e) radiating a furtherbeam directed on the agitated fragments and propagating within saidregion, detecting the further beam after propagation thereof within saidregion and deriving from the propagated further beam informationrelative to the size of the fragments.
 9. A lithotrite for focusedpulsed wave disintegrating of concretion within a region of the body ofa patient, said lithotrite comprising:(a) first means for generating,during short pulse periods, an elastic wave beam focused upon saidconcretion and having a predetermined high power adapted fordisintegrating the concretion into fragments, said first means includinga first electric pulse generator and a first focusing piezoelectrictransducer coupled to said first generator; (b) second means forradiating a pulsed acoustic signal beam, said second means including asecond electric pulse generator and a second piezoelectric transducer;third means connected to said second transducer for sweeping said signalbeam across said region; (d) fourth means connected to said secondtransducer for receiving echoes of the acoustic signal beam reflected insaid region; (e) fifth means for forming real time images of said regionby displaying said echoes; (f) sixth means for substantially reducingthe power and the pulse frequency of said first electric pulsegenerator, whereby said first means will generate further pulsed andfocused elastic waves adapted for agitating the fragments, (g) seventhmeans for disconnecting said second transducer from said second pulsegenerator and from said third means, whereby said second transducer willreceive further echoes of the further pulsed and focused elastic wavesreflected by the agitated fragments and (h) A type visual display meansfor displaying said further echoes to derive information relative to thesize of the fragments.
 10. The lithotrite of claim 9, said lithotritefurther comprising:(i) Doppler emitter receiver means for generating anelectric pulsed wave having a predetermined carrier frequency, saidDoppler emitter receiver means being coupled to said second transducer,whereby the second transducer will radiate a further pulsed acousticsignal beam directed on the agitated fragments and receive echoes ofsaid further acoustic signal beam having a further carrier frequencywhich differs from said predetermined carrier frequency and (j) meansfor deriving from the difference between the predetermined carrierfrequency and the further carrier frequency information relative to thesize of the fragments.
 11. The lithotrite of claim 10, wherein saidelectric pulsed wave beam has a pulse frequency which is a multiple ofthe pulse frequency of said further pulsed elastic waves and saidelectric pulsed wave beam and said further pulsed elastic waves aresynchronized.